Dear Crash maintainers,

We want to improve the crash_tool for the case that need offline cpu  register info even Kdump without crash_notes.

For one thing,  we will prepare a Kdump with all CPU register info in ELF note.
For another thing, we need to modify crash_tool and make it support adding offline cpu register info even Kdump without crash_notes.

We prepare a patch for the case with ARCH=arm64. 
It is verified with our kdump without crash_note and can get all cpu register.
Please take your time to review our patch and look forward to receiving your comments.

Patch detail as below

--- crash-7.3.0/arm64.c2021-04-27 16:01:07.000000000 +0800
+++ crash-7.3.0.mod/arm64.c2021-06-15 17:13:54.037273227 +0800
@@ -3667,8 +3667,41 @@ arm64_get_crash_notes(void)
 ulong *notes_ptrs;
 ulong i, found;
 
-if (!symbol_exists("crash_notes"))
+if (!symbol_exists("crash_notes")) {
+if (DISKDUMP_DUMPFILE() || KDUMP_DUMPFILE()) {
+if (!(ms->panic_task_regs = calloc((size_t)kt->cpus, sizeof(struct arm64_pt_regs))))
+error(FATAL, "cannot calloc panic_task_regs space\n");
+
+for  (i = found = 0; i < kt->cpus; i++) {
+if (DISKDUMP_DUMPFILE())
+note = diskdump_get_prstatus_percpu(i);
+else if (KDUMP_DUMPFILE())
+note = netdump_get_prstatus_percpu(i);
+else {
+error(WARNING, "cpu %d: cannot find NT_PRSTATUS note\n", i);
+continue;
+}
+
+/*
+ * Find correct location of note data. This contains elf_prstatus
+ * structure which has registers etc. for the crashed task.
+ */
+offset = sizeof(Elf64_Nhdr);
+offset = roundup(offset + note->n_namesz, 4);
+p = (char *)note + offset; /* start of elf_prstatus */
+
+BCOPY(p + OFFSET(elf_prstatus_pr_reg), &ms->panic_task_regs[i],
+      sizeof(struct arm64_pt_regs));
+
+found++;
+}
+}
+if (!found) {
+free(ms->panic_task_regs);
+ms->panic_task_regs = NULL;
+}
 return;
+}
 
 crash_notes = symbol_value("crash_notes");


Thanks,
James Hsu

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